It’s three days ahead of Apple’s scheduled “Back to the Mac” media event, but photos obtained by Engadget show a possible next-generation MacBook Air notebook with a unibody frame and what appears to be for a 13.3″ screen. The computer appears to have USB plugs on both the left and right sides, Mini DisplayPort and an SD card reader.

Engadget’s source claims the rest of the machine is also unibody, including the “large single mouse button,” but the screen will keep the current MacBook Air style, instead of the “edge-to-edge glass with black edges” that current MacBook Pro models have.

The laptop allegedly runs the same 1.86 GHz Intel Core 2 Duo processor as the current MacBook Air notebook, which could demonstrate that the photos are of an early prototype. Engadget’s source claims “the model dates back to at least April.”

The unverified photos represent “just one SKU,” so Apple may have something else in store as well, wrote author Paul Miller.

Additional sources have claimed that Apple will release a smaller 11.6″ MacBook Air this Wednesday at the company’s “Back to the Mac” special event.

Another source familiar with the matter believes the smaller form factor will forgo conventional hard-disk drive (HDD) or solid state drive (SSD) storage options in favor of an “SSD Card”, though details are still vague as to this possible feature.

Stay tuned for additional details as they become available and let us know what you think of the photos: